Somewhere along the line from "The Sopranos" to "The Wire," HBO executives must not have been paying much attention to trash television and its various ups, downs and boring middle points.

You know, like Tom Green. And "Jackass."

Interesting moments, sure. But nothing memorable. In fact, the public, of a certain age, never tuned in. And those who did, sensing in themselves an appreciation for stupidity but not necessarily a need to wallow in it, moved on.

Yes, the halcyon days of Tom Green. Here yesterday (or was it the day before?), gone today.

That may also be true of "Da Ali G Show," HBO's new late-night series, which premieres tonight, right after Bill Maher. A major hit on British television, Ali G is a "hip-hop journalist," the comedic concoction of Sacha Baron Cohen, who seems to be simultaneously spoofing white-boy hip-hop assimilation and how the over-the-top ludicrousness of its presentation plays in society.

It's a nice gimmick, actually.

Too bad the results seem so childishly undeveloped, as Baron Cohen seems content to make everything a sex or scatological joke. You have to wonder -- out loud, sometimes -- whether HBO really thinks this is a quality addition to the lineup or rather something from the "Real Sex" school of programming where you don't have to be too proud of it but, damn, the people love it.

Baron Cohen, apparently so enamored of his per sona (witnessed first in this country as a limo driver in a Madonna video), prefers to stay in character with the press. Not that he met the press recently, when HBO presented its midseason wares. That might also be a sign of something.

SPOOFS PEOPLE IN POWER

"Da Ali G Show" can, however, be ridiculously funny at different times. Nobody's saying Tom Green didn't have his moments, either. Or are they? But the point is, any person with cable has seen this kind of comedy before so it's not as if HBO has gone out and gotten itself something special. It has imported Ali G to the United States and let him loose to spoof unwitting Americans, usually people in power (politicians) or those gullible enough to be made sport of on camera (religious people, etiquette teachers, etc.).

Take away the British hype -- and at Baron Cohen's peak it was intense and immense, though people there are tiring of him now -- and you've got "JKX: The Jamie Kennedy Experiment." That's a WB show. And a good one, just not one many people watch.

The WB and HBO are owned by the same company. You'd think a deal could have been struck during a management retreat and there'd be no work-visa issues.

Perhaps it's a foolish approach to hold HBO to higher standards. There's no real fault in bringing Ali G to these shores and turning him loose on the people who created hip-hop and revel in it. Maybe it was merely good business - - tapping into a proven hit and trying to translate it. Hey, all the networks are doing it.

But there's a perception, and a pretty accurate one, that HBO will soon be in the market for the next big thing, given that its current big things, "The Sopranos" and "Sex and the City," are both going away next season.

So, as selective as HBO is about adding new original programming, it's not out of the question to think that maybe its executives believed that Ali G was,

if not the answer, some kind of answer.

Additionally, every time HBO adds a new series, there's this immense expectation. People are even excited by the return of Bill Maher, who not long ago, and on a broadcast network, was a pompous, gaseous, unfunny windbag. At HBO, expectations are such that Maher may pull a Gregor Samsa and become hilarious.

It's pretty clear that, despite its moments, "Da Ali G Show" is not going to be HBO's next defining series. And, given its almost low-key introduction, maybe HBO never intended it to be. There's just this high-standards issue that dogs the channel (everyone should be so lucky), and a British Tom Green isn't really what anyone expected.

Let's give Baron Cohen some credit, however. Ali G is a great character, and he leaves a lasting impression. He's an over-stylized hip-hop man on the street, but the effect is so clearly off it hints that Ali G really isn't a man of the street and has no credentials other than what he's dreamed up in his mostly empty head.

Again -- superb.

Two lesser Baron Cohen characters are Borat, a TV reporter from Kazakstan, and Bruno, an Austrian fashion reporter. These two suffer from lack of depth and one-note jokes that the American audience has seen in a number of guises and done far better by Andy Kaufman and Mike Myers, to name just two.

.5 In the debut, Ali G gets to go through training with the Philadelphia Police Department, including arresting some faux criminals: "Put up yous hands otherwise yous going to be shot by us." Most of it's funny. Some of it's dumb.

Borat getting dating tips is also sometimes funny, until you realize that the hokey accent and mannerisms always play to the same punch line -- a sex joke. Bruno shows up during New York's Fashion Week. It's boring. Then Ali G interviews former Attorney General Dick Thornburgh, and, as with his interview next week with, yes, it's true, former U.N. Secretary-General Boutros Boutros- Ghali, the juxtaposition is ridiculous and humorous.

GOOFS GET OLD

But only fleetingly. That's because it's too easy -- these men have, through some kind of misplaced generosity, decided to answer Ali G's questions,

which they can barely understand. When he makes fun of them, they don't get it. That's good for a few goofs, but it's tiring and, let's face it, needlessly cruel.

There's no question that Sacha Baron Cohen is talented. And it may prove unwise to discount the tremendous popularity he and his Ali G character achieved in the United Kingdom. But the concept is hardly original to an American audience and, unfortunately, plays well under the acceptable level of greatness we've all come to expect from HBO.